Which RAID with 8-8-4-4 TB Drives

[wblock]

You mean stripe two 4T drives to make a third 8T vdev? It *could* be done, but... that 4+4T vdev is twice as likely to fail as a single 8T drive. In theory. It could give you 16TB (sorta) on a RAIDZ1, but RAIDZ1 is not recommended for arrays of that capacity due to resilvering time. So... how valuable is your data, and how lucky do you feel?

 

[danb35]

Could I not leave the the two 8 TB drives the way they are, Vdev the 4tb drives and then setup a RaidZ1?

No.

is this a horrible idea to get an extra 4 TB out of my setup.

If it were possible, it would be a horrible way to do it.

 

[Jrod696]

That was a quick answer, and to answer your question, im not a lucky guy, hence the concern about redundancy. Although my important data is truly backed up to another location I would be in a pretty bad mood if I lost my data in general.

I think I will stick with the dual mirrors and stripe across and be happy with 12tb. Thanks again.

 

[Jrod696]

Well I want to thank everyone for their help, I got everything installed and I kinda felt like I knew what I was doing, One surprising thing I did notice is that it is striping the data evenly as I move it all from my old NAS. I didnt think it would, I figured as other said it would use more of the 8TB first but that does not appear to be the case

 

[Stux]

It works by spreading the data to the disks that come back for more data first... so the disks are probably performing about equal at this stage.

As you fill up the array, the 4TB disks will slow down relative to the 8TB disks, as the speed of a disk drops circa 50% across its surface... and you will move across the surface faster.

This should cause the writes to balance out as the first mirror slows down... more writes will tip towards the 8TB disk...

Relax :)

 

[Jrod696]

I am going to Necro my own post since it all ties together,
I just got 2 more 8TB drives, can I mirror them and add them to my vdev without any issue or is it going to go horribly wrong?

OR I do have all the data backed up,
would it be better to Raidz the 4x8tb's and mirror the 2x4tb's and then vdev them together?

What is the safest route for data security if a drive should fail.

 

[danb35]

can I mirror them and add them to my vdev

No, but you can add a new mirrored vdev to your pool, which is probably what you meant.

 

[gpsguy]

Follow @danb35 's advice.

Since you have a backup, in theory you could start over with a new RAIDzX vdev (containing 4x8TB) and extend the volume with a mirrored pair of 2x4TB. With 8TB drives, we don't recommend RAIDz1. So, even if you went with one RAIDz2 vdev and striped in the mirrrored vdev, your storage capacity would be the same as having 3 mirrored vdevs.

The other issue is that we don't recommend mixing vdev types within a given pool. If you are using RAIDz2 in a pool with mulitple vdev's, each vdev should be of the same type (and width).

If you are thinking about buying another pair of 8TB drives in the near future, another option would be destroy the pool and create a 6 disk RAIDz2 pool with 4x8TB and 2x4TB. The downside is that you'll only realize 4TB of space on your 8TB drives, but even with the loss of any two drives, your pool would survive. Down the road, you could replace the 4TB drives with 8TB drives and after both have been replaced and resilvered, your storage would automatically expand, ie. you'd get the full use of all your 8TB drives.

OR I do have all the data backed up,
would it be better to Raidz the 4x8tb's and mirror the 2x4tb's and then vdev them together?

 

[Jrod696]

I think for the sake of simplicity and future growth I am going to leave the 2x8 mirrored and the 2x4 mirror and just mirror the new 2x8 and then add them into the pool, that way I have the redundancy and if any one drive fails I dont have to restore from backup and I fall within the recommendations of keeping things the same.